The present invention relates generally to orthopedic instrumentation and more specifically to internal fixation devices.
Orthopaedic fixation devices may be used, for example, to stabilize an injury, to support a bone fracture, to fuse a joint, or to correct a deformity. The orthopaedic fixation device may be attached permanently or temporarily, and may be attached to the bone at various locations, including implanted within a canal or other cavity of the bone, implanted beneath soft tissue and attached to an exterior surface of the bone, or disposed externally and attached by fasteners, such as screws, pins, and/or wires. Some orthopaedic fixation devices allow the position and/or orientation of two or more bone pieces, or two or more bones, to be adjusted relative to one another. Orthopaedic fixation devices are generally machined or molded from isotropic materials, such as metals, including titanium, titanium alloys, stainless steel, cobalt-chromium alloys, and tantalum.
Although metal implants have been used for over a century, some problems still remain. For example, there is a stiffness mismatch between a metal implant and bone. This sometimes leads to stress shielding and bone loss. Additionally, many patients are allergic to metallic implants. Finally, some metals have a significant acquisition lead time, which may disrupt manufacturing operations.
It is often necessary to place an orthopaedic fixation device relative to bone. Currently, there are two main techniques for obtaining correct orthopaedic fixation device depth within an intramedullary canal of a bone. The first and oldest is the surgeon using radiography to visually align the hole in the orthopaedic fixation device with the femoral head and neck. There is difficulty in identifying the axis of the hole in the orthopaedic fixation device with which to align with the femoral head and neck. The second and newer method is the use of alignment arms/jigs that are attached to a drill guide. A C-arm is used to achieve a radiographic view of the implant and drill guide being placed in the bone. The alignment arm is attached to the drill guide and extends out on the anterior side of the patient. The arm contains radio-opaque markers that are visible on the radiograph. The marker shows the projection of the fastener that is to go through the orthopaedic fixation device and into the femoral head, and the surgeon uses the projection to align the implant with the femoral head.
To obtain version this is normally performed by the surgeon using a radiograph to visually determine the correct rotation of the orthopaedic fixation device relative the femoral head and neck. In a medial-lateral view, the surgeon attempts to align the screw hole or nail profile with the femoral neck and head. Another method to attain appropriate version is with use of a drill guide that contains a set of plates or a metal wire imbedded in it that the user aligns with the femoral head and neck using radiography.